Tond-s nails 3 ^ i 



Limn£eida3, but the more typical characters of that 

 family are seen in the genus Limn cm, where both 

 animal and shell are twisted to the right. They 

 are familiarly known as Pond-snails, all the species 

 being restricted to still, shallow waters. The animal 

 has a prominent head with short, flattened, triangular 

 tentacles. From the distant position of the sexual 

 organs one individual may be united with two 

 others at the same time, and it is by no means 

 unusual to see a number of Pond-snails so connected 

 in one chain. The character of the teeth on the 

 radula may be gathered from this figure of the middle 

 portion of a single row ; there is a small central 

 tooth with 59 laterals on each side, and there are 



Portion of row of teeth from radula of Great Pond-snail 



110 such rows on the radula, making a total of 



12,210. 



The Great Pond-snail (L. stagnalis) offers the 

 advantages of being larger than, and readily dis- 

 tinguished from, the other members of the genus, 

 so will serve as a good type. The animal is coloured 

 yellowish grey ; its head large and adorned by long 

 tentacles which end in slender points; the broad 

 foot edged- with yellow. The yellow -brown or 

 greyish shell is a couple of inches long, and half 

 as broad; thin when compared with marine shells, 

 but tolerably solid for a Pond-snail. It is covered 

 by a thin epidermis, which frequently decays on 

 the older portion of the shell and allows the 



